Climate in earth's polar regions is incredibly complex, varying simultaneously on a number of different timescales for a number of different reasons (Venegas and Mysak, 2000). Against this backdrop of natural variability, it is extremely difficult to identify the anthropogenic greenhouse signal that has been predicted to result from the burning of fossil fuels. The task is further complicated because many of the records that do exist contain only a few years to a few decades worth of data; and they yield different trends depending on the period of time studied. Such is also the case with the observational records of polar sea ice.
Consider, for example, the study of Johannessen et al. (1999), who analyzed trends in Arctic sea ice extent and thickness over the 1978-1998 and 1978-1991 time periods. From 1978 to 1998, they found that the area of Arctic sea ice decreased by about 14%; and the high correlation (r = 0.88) between ice thickness and ice area between 1978 and 1991 suggests that ice thickness may have declined over the larger period as well. These findings led the authors to conclude that "the balance of evidence thus indicates an ice cover in transition" and that "if this apparent transformation continues, it may lead to a markedly different ice regime in the Arctic." Similar sentiments have been expressed by Vinnikov et al. (1999).
Reading Johannessen et al.'s assessment of the situation, one is left with the impression that a relatively consistent and ongoing transformation (a persistent reduction in the area and thickness of Arctic sea ice) is, in fact, in progress. However, according to their own data, this assessment is highly debatable and possibly false. In viewing their plots of sea ice area and thickness (their Figure 2), for example, it is readily evident that the decline in both of these parameters did not occur smoothly over the 20-year period of study. In fact, essentially all of the drop in both parameters occurred rather abruptly over a single period of not more than three years (87/88-90/91) and possibly only one year (89/90-90/91). Furthermore, it could be argued from their data that from 1990/91 onward, sea ice area in the Arctic may have actually increased.
Data published by Winsor (2001) tell a different story, revealing that "mean ice thickness has remained on a near-constant level around the North Pole from 1986-1997." Using data obtained from six submarine cruises that traversed the central Arctic Basin, Winsor found that mean Arctic sea ice thickness remained "almost constant," and that sea ice thickness centered around the North Pole showed little variability and a "slight increasing trend" in the 1990s. Additionally, data from the Beaufort Sea region revealed "no significant trend" in sea ice thickness over the same time period. Furthermore, Parkinson (2000) utilized satellite-derived data of sea ice extent to calculate changes in this parameter for the periods 1979-1990 and 1990-1999, reporting that in seven of the nine regions into which the Arctic was divided for the analyses of this study the "sign of the trend reversed from the 1979-1990 period to the 1990-1999 period," indicative of the ease with which significant decadal trends are often reversed in this part of the world.
Other studies have analyzed Arctic sea ice parameters beyond the observational record using proxy data sources. Omstedt and Chen (2001), for example, obtained a proxy record of the annual maximum extent of Arctic sea ice in the region of the Baltic Sea over the period 1720-1997. In analyzing the record, they found a significant decline in sea ice occurred around 1877. Furthermore, they reported finding greater variability in ice extent in the colder 1720-1877 period than in the warmer 1878-1997 period.
Also in the Baltic Sea, Jevrejeva (2001) reconstructed an even longer record of sea ice by examining historical data for the observed time of ice break-up between 1529 and 1990 in the northern port of Riga, Latvia. The long date-of-ice-break-up time series was best described by a fifth-order polynomial, which identified four distinct periods of climatic transition: (1) 1530-1640, warming with a tendency toward earlier break-up of 9 days/century, (2) 1640-1770, cooling with a tendency toward later break-up of 5 days/century, (3) 1770-1920, warming with a tendency toward earlier break-up of 15 days/century, and (4) during the period of rapid rise in greenhouse gas emissions, 1920-1990, a cooling with a tendency toward later break-up of 12 days/century.
In a separate proxy study, Grumet et al. (2001) examined Arctic sea ice cover in the region of Baffin Bay over the past 1000 years, where they found that following a period of reduced sea ice during the 11th-14th centuries, enhanced sea ice conditions prevailed during the past 600 years. As for the past 100 years, they note that "despite warmer temperatures during the turn of the century, sea-ice conditions in the Baffin Bay/Labrador Sea region, at least during the last 50 years, are within 'Little Ice Age' variability," suggesting that sea ice conditions there have not yet even emerged from the range of natural variability characteristic of the Little Ice Age.
Lastly, Comiso et al. (2001) examined satellite imagery to analyze and quantify a number of attributes of the Odden ice tongue - a winter ice cover phenomenon that occurs in the Greenland Sea with a length of about 1300 km and an aerial coverage of as much as 330,000 square kilometers - over the period 1979-1998, further utilizing surface air temperature data from Jan Mayen Island, located within the region of study, to infer the behavior of this phenomenon over the past 75 years. Trend analyses revealed that the ice tongue has exhibited no statistically significant change in any of the parameters studied over the short 20-year period. However, proxy reconstruction of the Odden ice tongue for the past 75 years revealed the ice phenomenon to have been "a relatively smaller feature several decades ago," due to warmer temperatures that prevailed at that time.
When considering all of the above results, it is difficult - if not impossible - to accept the climate alarmist position that Northern Hemispheric sea ice is rapidly disintegrating in response to CO2-induced global warming. Rather, the oscillatory behavior observed in so many of the sea ice studies suggests, in the words of Parkinson (2000), "the possibility of close connections between the sea ice cover and major oscillatory patterns in the atmosphere and oceans," including "connections with: (1) the North Atlantic Oscillation (e.g., Hurrell and van Loon, 1997; Johannessen et al., 1999; Kwok and Rothrock, 1999; Deser et al., 2000; Kwok, 2000, Vinje, 2001) and the spatially broader Arctic Oscillation (e.g., Deser et al., 2000; Wang and Ikeda, 2000); (2) the Arctic Ocean Oscillation (Polyakov et al., 1999; Proshutinsky et al., 1999); (3) a 'see-saw' in winter temperatures between Greenland and northern Europe (Rogers and van Loon, 1979); and (4) an interdecadal Arctic climate cycle (Mysak et al., 1990; Mysak and Power, 1992)." The likelihood that Arctic sea ice trends are indeed the product of such natural oscillations, Parkinson continues, "provides a strong rationale for considerable caution when extrapolating into the future the widely reported decreases in the Arctic ice cover over the past few decades or when attributing the decreases primarily to global warming."
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